Lost converter lockup

Tiredmechanic23 · Sep 7, 2024

So 2016 LS, trans has about 8k on it built by TKR Transmission (Tim King Racing) with a billet 4 clutch PATC converter. On my way home from work the other day I noticed it slipped out of lockup so I manually dropped it to 4th and finished getting home. Temps didn't exceeded 170 thankfully. So I had a spare new stock converter and swapped it in with a fresh turbine O ring and went for a drive. Same thing, works for a few minutes then kicks out. This time I guess I had traveled far enough it tossed a code. P0741 for tcc stuck off.

So is it safe to assume that I need to likely replace the TCM/solenoids?

Geotrash · Sep 7, 2024

Tiredmechanic23 said:
So 2016 LS, trans has about 8k on it built by TKR Transmission (Tim King Racing) with a billet 4 clutch PATC converter. On my way home from work the other day I noticed it slipped out of lockup so I manually dropped it to 4th and finished getting home. Temps didn't exceeded 170 thankfully. So I had a spare new stock converter and swapped it in with a fresh turbine O ring and went for a drive. Same thing, works for a few minutes then kicks out. This time I guess I had traveled far enough it tossed a code. P0741 for tcc stuck off.

So is it safe to assume that I need to likely replace the TCM/solenoids?

@NickTransmissions may have some insight for you.

Take a look at his 6L80 information thread also:
Thread 'GM 6L80 Transmission Information Thread'
https://www.tahoeyukonforum.com/threads/gm-6l80-transmission-information-thread.141927/

Tiredmechanic23 · Sep 8, 2024

Thank you, I'll look it over.

NickTransmissions · Sep 9, 2024

Tiredmechanic23 said:
So is it safe to assume that I need to likely replace the TCM/solenoids?

There's no such thing as a 'safe' assumption...I can tell you what I'd do if you brought the unit to me with the above backstory:

Prereq - scan the vehicle for DTCs stored; if trans was still in the vehicle, drive it with the scanner plugged in to view live engine and transmission data to see what shows up.

Once vehicle is off the road, I'd do the following:

1. Test the TEHCM in the vehicle's presence using the Kent Moore TEHCM Bench Test Block - this confirms each individual captured solenoid is actually functioning when energized
2. Continuity test each solenoid and pressure switch on the TEHCM

If the TEHCM passed both tests, I'd replace the diaphragms and their respective seals on the pressure switches and move on; if any failed, I'd order a new GM TEHCM

3. Tear down the valve body paying close attn to any valves either dragging or hanging up in the bore; clean VB and all valves/components and reassemble the valve body; I'd also inspect check balls
4. Vacuum test the valve body in its entirety, paying close attn to the TCC regulator valve

If the valve body failed any vacuum tests and replacement valves from Sonnax or Transgo have not been installed, I'd install replacement corrective valves, plugs or whatever it needed

If the valve body already has a corrective kit but it's still to worn, I'd order a reman valve body to replace it

If the valve body and TEHCM both pass, the transmission would have to come out and be thoroughly inspected

Tiredmechanic23 · Sep 9, 2024

NickTransmissions said:
There's no such thing as a 'safe' assumption...I can tell you what I'd do if you brought the unit to me with the above backstory:

Prereq - scan the vehicle for DTCs stored; if trans was still in the vehicle, drive it with the scanner plugged in to view live engine and transmission data to see what shows up.

Once vehicle is off the road, I'd do the following:

1. Test the TEHCM in the vehicle's presence using the Kent Moore TEHCM Bench Test Block - this confirms each individual captured solenoid is actually functioning when energized
2. Continuity test each solenoid and pressure switch on the TEHCM

If the TEHCM passed both tests, I'd replace the diaphragms and their respective seals on the pressure switches and move on; if any failed, I'd order a new GM TEHCM

3. Tear down the valve body paying close attn to any valves either dragging or hanging up in the bore; clean VB and all valves/components and reassemble the valve body; I'd also inspect check balls
4. Vacuum test the valve body in its entirety, paying close attn to the TCC regulator valve

If the valve body failed any vacuum tests and replacement valves from Sonnax or Transgo have not been installed, I'd install replacement corrective valves, plugs or whatever it needed

If the valve body already has a corrective kit but it's still to worn, I'd order a reman valve body to replace it

If the valve body and TEHCM both pass, the transmission would have to come out and be thoroughly inspected

Great info, thank you. Valve body has had any corrections and improvements made. The entire trans was built as much as it can be. It had 100k on it when pulled for a previous built converter failure (had 100k on it as well) where the hub broke and splines stripped.

The trans has all new pump including bell housing. TECHM was tested by the builder and at the time did pass or it would have been replaced.

Only DTC is the P0741 and I have tried another spare new converter already. Vehicle can be driven and I have no issues getting live data. What PIDs am I looking for and what values? Would a data log on EFI Live be of any help?

As far as testing the valve body of the TECHM I don't have the ability to do the vac test nor the bench test as I'd have to completely down the vehicle at the moment and that is hard to do right now unfortunately.

NickTransmissions · Sep 9, 2024

Tiredmechanic23 said:
Great info, thank you. Valve body has had any corrections and improvements made. The entire trans was built as much as it can be. It had 100k on it when pulled for a previous built converter failure (had 100k on it as well) where the hub broke and splines stripped.

The trans has all new pump including bell housing. TECHM was tested by the builder and at the time did pass or it would have been replaced.

Only DTC is the P0741 and I have tried another spare new converter already. Vehicle can be driven and I have no issues getting live data. What PIDs am I looking for and what values? Would a data log on EFI Live be of any help?

As far as testing the valve body of the TECHM I don't have the ability to do the vac test nor the bench test as I'd have to completely down the vehicle at the moment and that is hard to do right now unfortunately.

You're welcome.

PIDs to watch on the scanner are transmission shift speeds (should be less than a second), TCC slip speed (RPM) at higher duty cycles - slip speeds should be less than 10 RPM when the TCC is enabled (gears 2-6).

Also look at the MAF, TPS and other engine sensor/switch data streams to see if anything odd is observed as TCC can be commanded to lock and unlock. I always replace the TEHCMs when I overhaul 6L transmissions as they can test perfectly fine at the time then take a dump 20k miles later or so just because it's time. You can continuity check the TCC solenoid to see what resistance value you get but to positively diagnose that as the true source of the problem, you would need to do the full TEHCM bench test.

Same with the valve body...I did a video on valve body testing folks an idea of what's involved, what to look for and how to determine when corrective action may be needed for these VBs:

Tiredmechanic23 · Sep 10, 2024

TPS is smooth and corelation between pedal and TB looks good. MAF at idle is about 8 grams and goes up from there. I do tend to use MAF cleaner every 50-75k miles or after it sits.

Slip speed though is more than 10 RPM. I am tuned so tcc only locks above 4th. But it slips by much more than 10rpm.

As far as TECHM replacement goes. This is the OE TECHM and has 200k total on it.

Without being able to do the full proper bench test for the TECHM I may just need to order one to have on hand. I don't have any trans shops near me to carry it to for proper testing unfortunately. I'll verify the live data again on the way to work this morning.

Before I forget I have a 6.2 intake and TB and both engine and transmission tune are from Blackbear.

NickTransmissions · Sep 10, 2024

Tiredmechanic23 said:
TPS is smooth and corelation between pedal and TB looks good. MAF at idle is about 8 grams and goes up from there. I do tend to use MAF cleaner every 50-75k miles or after it sits.

Slip speed though is more than 10 RPM. I am tuned so tcc only locks above 4th. But it slips by much more than 10rpm.

As far as TECHM replacement goes. This is the OE TECHM and has 200k total on it.

Without being able to do the full proper bench test for the TECHM I may just need to order one to have on hand. I don't have any trans shops near me to carry it to for proper testing unfortunately. I'll verify the live data again on the way to work this morning.

Before I forget I have a 6.2 intake and TB and both engine and transmission tune are from Blackbear.

That TEHCM has quite a lot of miles on it, lol...You can continuity test it via a DVOM then used a fused 12v power supply to energize the TCC solenoid to see if it's responding but that's only going to confirm that it's electrically functional...The status of its mechanical function will still be unknown without that bench test equipment.

Additionally, you may have a very worn TCC regulator valve in the lower valve body...If you're going to do anything beyond just DVOM-testing the solenoid in the TEHCM, I'd drop the valve body and install a Sonnax Zip kit or Transgo's Reprogramming kit for those transmissions. You won't be able to install any of the parts/valving for the pump since the trans has to be apart for that but at least you can refresh/correct the valve body if need be.

Up to you if you want to sink the time and money into it without knowing whether or not it will fix the problem...

Tiredmechanic23 · Sep 11, 2024

ess

NickTransmissions said:
That TEHCM has quite a lot of miles on it, lol...You can continuity test it via a DVOM then used a fused 12v power supply to energize the TCC solenoid to see if it's responding but that's only going to confirm that it's electrically functional...The status of its mechanical function will still be unknown without that bench test equipment.

Additionally, you may have a very worn TCC regulator valve in the lower valve body...If you're going to do anything beyond just DVOM-testing the solenoid in the TEHCM, I'd drop the valve body and install a Sonnax Zip kit or Transgo's Reprogramming kit for those transmissions. You won't be able to install any of the parts/valving for the pump since the trans has to be apart for that but at least you can refresh/correct the valve body if need be.

Up to you if you want to sink the time and money into it without knowing whether or not it will fix the problem...

The valve body and pump mods were dome when the build was done. TKR won't build one without the modifications, I'd have to double check but I'm 99% sure the valve body was replaced as well due to wear on the old one (was also modified)

As far as verifying the electrical part of it, that's what I was afraid of. I know even if the electrical portion is good the solenoid may not actually be ok. I'd love to bench it but without the proper equipment I'm SOL on that.

As far as tossing parts goes, it's far from ideal considering TECHM prices but lacking the equipment to test or a shop that can do it for me here, I don't have a lot of options.

Edit: was able to get ahold of TKR Transmission today, every time I've called it's gone to VM but it was always later in the day as well. They told me not to stress it and that they have a few spare good TECHMs around to send them my software info and they would just send one my way to try out.

So while a TECHM is a parts toss, at least it won't be a financial loss now. They have always been great to work with and I'm glad that continues.

Lost converter lockup

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